Recently, a new technology for fabricating integrated optical components has been developed by depositing doped-silica waveguides on silicon substrates by such techniques as chemical or plasma etching, ion milling, sputter etching, and chemically assisted ion milling. See for example, J. T. Boyd et al., Optical Engineering, Vol. 24, No. 2, pp. 230-4 (1985) and F. S. Hickernell, and Solid State Technology, Vol. 31, No. 11, pp. 83-8 (1988). Advantageously, this technology affords the potential to make optical devices that are compact, of greater complexity, and lower in cost than those devices fabricated from fiber or microoptics components.
In the prior art, various passive optical components have been made using the above silica on silicon technology in which optical waveguides are deposited on a base layer called a "hipox" formed by the oxidation of silicon under high pressure steam. Typically, anisotropic etching is utilized to define the core structure comprising, for example, phosphosilicate glass or P-doped silica. Further, with a thin cladding layer of silica (SiO.sub.2) covering the core, low loss channel waveguides are readily fabricated on silicon, which then may be configured to produce many useful integrated optical devices for communications and signal processing, such as Bragg reflectors, four channel multiplexers, polarization splitters and array star couplers. See, for example, C. H. Henry et al., Journal of Lightwave Technology, Vol. 7, 1379-85 (1989), Y. Shani et al. Appl. Phys. Lett., Vol. 56 pp. 120-1 (1990), and U.S. Pat. No. 4,904,042.
While these devices exhibit excellent performance, many of the components therein, namely the waveguides, are highly sensitive to the environment due to the relatively thin silica or SiO.sub.2 cladding layer. The coating, that is the cladding layer, which is about 4 .mu.m thick does not provide sufficient optical confinement for the evanescent field radially extending from core, thereby allowing it to deleteriously interact with the environment. For example, touching the upper surface of the component dramatically changes the device performance. Although a much thicker cladding layer could be deposited, on the order of approximately 10 .mu.m, such a thick coating either tends to crack due to stress or prohibitively takes a very long time, on the order of a day, to deposit. Equally important, in these devices, if one attempted to attach a fiber pigtail connector, such as an array of fibers using silicon v-grooves, in order to make them practical, an unstable situation results because connection could only be made to the silicon substrate and the thin cladding layer, thus, leaving the upper portion of the fiber pigtail connector hanging and prone to misalignment.